Flexible joint for an air drop hammer



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Patented Sept. 30, 1958 FLEXIBLE JOINT FOR AN AIR DROP HAMMER Carl W.Coslow, Los Angeles, Calif.

Application July 11, 1956, Serial No. 597,285

l Claim. (Cl. 287-85) This invention relates generally to air and/orsteam drop hammers, and more particularly to connecting rods for suchdrop hammers.

The service conditions under which modern air and steam drop hammersoperate, some of which will be described hereinafter, impose severebending moments on the connecting rods thereof, suicient to over-stressthe rod, and cause rapid fatigue and early failure. When the connectingrod fails, the hammer must be taken out of service for replacement, at acost, considering both the cost of the new rod, installation and losthammer time, as much as $3,000 to $4,000. The life of the hammer rods inlarge air or steam hammers is of the order of four hundred hours. Itwill be seen that hammer rod failure is a serious and costly occurrence.

It may accordingly be stated as the primary object of the presentinvention to provide an air or steam hammer connecting rod with a meansrelieving it of bending moment strains in service, to the end that suchrods will stand up practically indefinitely under service conditions.

In general, an air drop hammer as now known comprises essentially ananvil or base, two heavy side frames equipped with guides and gibs thatcan be moved in and out, i. e., towards and away from the center line ofthe hammer, a heavy hammer head or ram, and a connecting rod which isdriven into the head or ram and held by a tapered lit, a piston attachedto the upper end of the connecting rod which runs vertically through astuffing box to prevent the air from escaping around the rod, an aircylinder, and appropriate timing devices for admitting high pressure airunder the piston and exhausting that air from under the piston at theupper end of the piston stroke. The air pressure performs only onefunction, namely, to lift the weight of the ram through the connectingrod. The work done by the hammer is the blow of the guided, free fallinghead or ram. The ram may weigh thousands of pounds. The connecting rodthus performs nouseful function on the down stroke of the hammer. Itcomes into play only in the lifting of the head preparatory to its nextdown stroke.

Steam drop hammers are essentially similar, with the exception that onthe down stroke, steam pressure acts on the top of the piston to add tothe acceleration of gravity. At or near the bottom of the stroke,however, the steam pressure is relieved by suitable valvingarrangements, and the blow struck is owing entirely to the inertia ofthe accelerated hammer head.

The side frames on such hammers have adjusting arrangements includingslots and hold down bolts which permit the moving of these frames towardand away from the center line of the hammer. These frames moveindependently of one another in guides on the hammer base. The operatoris expected to adjust these frames to maintain proper clearance betweenthe guides and the hammer head at all times. However, this is not alwaysdone as it should be. For example, in the morning,

whenthe hammer is cold, the side frames should be brought in towards thecenter line to provide a properly close working clearance between thehammer head and the frame guides. As the hammer grows hot in service, itexpands, requiring that the frames be moved out to maintain properclearance. If this is not done, the hammer head becomes too tight in theguides, resulting in excessive friction, wear, and loss of proper hammerblow.

Hammer men operating on piece rate, in order to avoid shutdown time foradjustment, are found usually to set the clearance' too wide when thehammer is cold, with the result that the head is not adequately guidedand is free to move excessively from side to side. Passing over the factthat this condition of excessive play results in poor work owing tomismatch of dies, which under such conditions are not necessarily ingood alinement, such excessive play results in serious bending momentsbeing set up in the rod under certain common conditions of service. Thedies commonly are provided across their faces with various pairs ofimpressions for successive forging operations on the work piece, andwhile one of such pairs of impressions may be on the center line of therod, impressions on either side thereof are not. When these off-centerline impressions are used, a blow struck by the hammer head results inthe hammer head cooking in the assumed loose guides. Since the rod istightly mounted in the head at one of its ends, and constrained toalinement with the center line of the cylinder at its other end by thepiston and air cylinder, such cocking sets up severe bending moments inthe rod. T he repeated bending moment, and capability of bending underthe described conditions, results in undue fatigue of the rod and earlyfailure.

Again, even though proper spacing of the side frames with respect to oneanother be achieved, it is almost impossible, owing to the crude methodof moving the frames, to adjust them at exactly equal distances from thecenter line of the piston on the air cylinder. The piston and the upperend portion of the connecting rod are constrained to move on the centerline of the cylinder. But if the frames, even though properly spacedfrom one another, are not equally spaced from the center line of thecylinder, they guide the hammer head along an olfset center line, whichcondition sets up severe bending momentsV in the rod, in addition tocausing scoring of the rod as it passes through the stung box, wear onthe stung box, leakage, packing troubles, and expensive repair. Thedescribed bending of the, rod under these conditions contributes greatlyto fatiguev and early failure of the rod.

Bending strains on the rod also occur from still another cause. Theupper and lower die in the hammer must be lined up, one above the other,to prevent crosswise mismatch. The dies fit in dovetails in the hammerhead and anvil, and are held solidly in place by tapered keys driven inby a heavy ram. They must be very tightly locked in place to withstandthe jar of the hammer. It is a very diicult matter to exactly line upthese dies, one above the other, using wedges, shims, Sledge hammers,rams, etc., for the purpose. Commonly, the operator first achieves afairly close die alinement by such methods, and then moves the sideframes to obtain nal die alinement. This, however, throws the hammerhead out of alinement with the cylinder and piston, and again subjectsthe rod to bending moments, fatigue, and ultimate failure.

Finally, it is commonplace for the faces of the dies to be out ofparallel, one with the other. The pounding of the hammer, the effect ofthe hot metal, the shims, wedges, and the tits in the dovetail, alloperate to make it practically impossible to maintain perfectparallelism between the operating faces of the upper and lower dies.When dies that are out of parallel strike die to die, a bendingmomentrisV set up, the head tends to cock in the guides, which areusually' set fairly loose, and the resultant periodic bendingcontributes to fatigue and failure.4

The present invention, which provides relief for all of the conditionsmentioned hereinabove, comprises a flexible rubber coupling between'theconnecting rodv and hammer head. Such coupling permits cooking of thehammer head under the various misalinement conditions mentioned in theforegoing passages without setting up material bending moments in therod. That is to say, as the hammer head cocks upon striking a blow underthe-,several conditions described,-the exible rubber coupling readilydeforms to accommodate such action, leaving the rod itself insubstantially undisturbed alinement with its piston and cylinder. Theflexible coupling also furnishes accommodation for the condition broughtabout by side frame guides adjusted to proper spacing from one another,but unequally spaced from the true center line of the rod, piston andcylinder. Under such conditions, the coupling may compress suiiicientlyin a lateral plane to permit the hammer head to workV up and down easilyin the side frame guides, while the rod itself retains its alinementwith the piston and cylinder, so that, here again, bending strains arealleviated.

The invention will be further understood from the following detaileddescription of a present illustrative embodiment thereof, referencebeing had to the accompanying drawings, in which:

Fig. l is a perspective view of a conventional air drop hammer;

Fig. 2 is an illustrative diagrammatic view of an air drop hammer, partsin section and broken away;

Fig. 3 is a longitudinal sectional view of a connecting rod, flexiblecoupling and partially illustrated hammer head in accordance with theinvention; and

Fig. 4 is a plan view taken on line 4 4 of Fig. 3.

In the drawings, which show an air drop hammer for illustrativepurposes, and with particular reference first to Figs. l and 2, numeraldesignates a conventional air drop'hammer, having base or anvil 11, sideframes 12` adjustable toward and from one another along guideways 13,air cylinder 14, piston 15, piston rod 16, stung box 14a, hammer head orram 17, vertically guided by suitable guides 18 on side frames 12,hammer-carried die 19, and anvil mounted die 20.

The side frames will be understood to be arranged for adjustment of thedistance therebetween to follow expansion of the hammer head as aconsequence of heating during operation, and it will be furtherunderstood that elort is made by the operator to adjust these to beequally spaced from the center line or axis A-A of the air cylinder andpiston.

It can be readily appreciated from an inspection of Fig. 2 how unequalspacing of these side frames With respect to piston and cylinder centerline A--A' imposes severe bending lmoments on the rod. It can further bereadily appreciated how, in event of striking of the hammer against awork piece w in an oli-center position such as indicated will result incooking of the hammer head, with resulting bending strains in the rod,particularly when the side frames are adjusted With a certain loosenessor play between the hammer head and .the guides. And it can further -bereadily appreciated how non-parallelism of the striking faces ofthe diescan impose severe bending moments on the rod. Still further, it canreadily be appreciated that, even with proper spacing of the side'framesfrom one another, unequal spacing thereof from the center line of thepiston and cylinder results not only in bending 'of the rod, but scoringof the rod at the stuiiing box, wear on the stuing box, etc.

With reference now to Fig. 3, my improved connecting rodv is designatedgenerally a-t 25, and it will be understood that this rod is for use ina conventional drop hammer such as shown in Fig. l, and diagrammed inFig. 2. Y

The upper end portion of this rod (not shown) will accordingly beunderstood to run up through the usual stu'ing box and to beconventionally fitted to the piston within the air cylinder.

The partiially illustrated ram and hammer heady is again designated bythe numeral 17, and the exible coupling between the rod and head isdesignated generally at 26. Rod 25 has near its lower extremity atapered section 27, and its lower extremity is screw threaded to receivenut 28. Mounted on tapered section 27 is a steell coupling disk or plate29, and this disk is secured in posi-V tion by a washer 29a againstwhich the aforementioned nut is tightly set. As shown, the nut isslotted, and a locking pin 30 engaged with a selected slot secures thenut in tightened position.

Enveloping and bonded' tothe peripheral face 29b and upper and lowerfaces 29e and 29d, respectively, of disk 29, outside the yarea of therod and nut, is a flexible rubber coupling member 3-1, having Hat upperand lower faces, and a cylindrical periphery, as shown.

This coupling member 31 includes inside cylindrical surface 31acontacting disk surface 29h, downwardly facing inside surface 3111contacting face 29c of disk 29, and upwardly facing inside surface 31econtacting `face 29d of disk 29. n

The lower face 31d of this coupling member rests on an annular face 32aon the top of an annular upper portion 32 of a ram adaptor 33, therebeing a central recess 34 in the upper end of the adaptor for receptionof nut 28 and the lower extremity of rod 25. Adaptor k33 has a central,downwardly projecting-tapered shank 35 driven into a correspondinglytapered lbushing 36 set tightly into head 17. A coupling housing 37, inthe general form of an inverted cup, iits down over rubbercouplingmember 31, its inside surface 37a snugly engaging the periphery 31e kofthe latter, and slidably fitting over annular adaptor portion 32, withthe under face 38a of its top Wall 38 engaging the upper face 31f ofcoupling member 31. The lower rim of the cylindrical side Wall 39 ofthis housing cup, upon approximately 1,41" compression of couplingmember 31, engages an outwardly n extending annular flange 40 at thebase of adaptor 33; The cup side wall is drilled, as at 41,for aplurality of draw bolts 42, and these are adapted to engage in tappeddrill holes 43 in base ange 40. Tightening of the draw bolts to seathousing wall 39 on adaptor ange 40 compresses, and thus pre-loads, theexible rubber coupling member 31. When the draw bolts are in position, apair of key rods 45 are inserted in alined bores 46 and V47 in thehousing and adaptor, respectively, to secure the parts The flexiblecoupling as thus described relieves the rod of the describedmisalinement and misadjustrnent bending and wear strains. Any cooking ofthe hammer head upon striking a blow is accommodated by deformation ofthe Viiexible rubber coupling member 31, any bending forces transmitted`to the rod being entirely insignicant. In the event ofk the side frameguides being positioned to space the hammer head off-center from thecenter line of the cylinder and piston, the flexible coupling deforrnslaterally to permit the head to conform to the position of the guides,while'the rod remains in alinement with the cylinder and piston, and isunder no material strain as a consequence of the misalinement.l'naddition, the rod remaining in alinementV with the'cylinder andpiston, Wear on the rod, stuing box, etc., as a consequence of this typeof misalinement, is relieved. Summarizing briefly, it will be seen thatthe invention contemplates a ilexible, deformable rubber coupling memberbetween the rod and hammer head or ram, in such arrangement as permitscooking of the head with respect to the rod, withoutbending of the rod,as well as limited lateral displacement ofI the head with respect to therod, again without imposition of material bending strain on the rod.

I have now disclosed one present preferred embodiment of my invention.It will be understood, however, that various changes in design,structure and arrangement may be made without departing from the spiritand scope of the appended claim.

I claim:

A coupling for the connecting rod and ram of a drop hammer, comprising:a rod coupling means rigidly vconnected to an end of said rod, a ramcoupling means rigidly connected to said ram, said rod and ram couplingmeans having a range of lateral and angular movement relative to oneanother, and resiliently deformable rubber coupling means interposedbetween said rod and ram coupling means and having a surface held fastto said rod coupling means and another surface held fast to said ramcoupling means, with the portion of said rubber coupling means betweensaid surfaces acting by resilient deformation to accommodate limitedlateral and angular displacements of said ram relative to said rod froma normal centered and aligned position relative to the rod, and actingby vresilient restoration to return the displaced ram to `said normalposition.

References Cited in the file of this patent UNITED STATES PATENTS1,641,091 Minck Aug. 30, 1927 1,670,493 Clark May 22, 1928 1,720,592Fitzgerald July 9, 1929 1,812,464 Billings June 30, 1931 1,864,080 MadgeJune 21, 1932 1,957,021 Schneider May 1, 1934 2,079,460 Marty May 4,1937 2,098,703 Geyer Nov. 9, 1937 2,195,644 Fitzgerald Apr. 2, 19402,220,036 Fitzgerald Oct. 29, 1940 2,661,969 Thiry Dec. 8, 19532,794,661 Sears June 4, 1957 FOREIGN PATENTS 342,996 Great Britain Feb.12, 1931 828,471 Germany Jan. 17, 1952

